The probe is part of a broader SEC inquiry into possible insider trading by hedge funds in connection with the biggest healthcare deals of the last decade, the Journal said.

Britain's second-biggest drugmaker AstraZeneca <AZN.L> bought Maryland-based MedImmune in 2007, which was then one of the largest independent U.S. biotech companies, best known for the nasal spray flu vaccine FluMist.

Hedge fund industry heavyweight SAC has also come under the attention of federal prosecutors in New York and by Senator Charles Grassley of Iowa concerning its trading activities.

Grassley is reviewing 20 stock trades made by Steven Cohen's SAC over the last decade, while federal investigators have been investigating allegations of wrongful trading at the $14 billion star hedge fund for nearly four years.

A spokesman for AstraZeneca declined to comment on the matter. SAC Capital did not respond immediately to requests by Reuters seeking comment.